krystle campbell was one of those killed. her mother paid tribute to her. >> i cannot leave this has happened. she was such a hard worker in everything she did. >> boston is a city that mourns for its dead. tomorrow, president obama comes to sharon agreed, and to reassure a nation shaken by the attacks on the marathon. >> a busy day in the investigation where we do seem to have fixed the sound problems that we have with boston. lord trevelyan is there. we have been getting conflicting reports -- laura trevelyan is there. we have been getting conflicting reports. describe for us what we know and what we do not know. time, thereoint in are two things we know. boston police and the fbi have said that no arrests have been made in connection with this case. and we also understand that a press conference with information from the police and the fbi was do about half an hour ago, but was postponed. that is due this evening. those are the two things we know. the rest of the realm of speculation and contradictory information is someth